In recent years, vehicles that incorporate a start-stop function have been increasing in number. A battery with which such a vehicle is equipped is put under high load. For this reason, it is important to monitor the status of the battery.
For example, Patent Literature 1 discloses a device equipped with a small full-scale current sensor to estimate the status of a battery for starting the engine. This device estimates the status of the battery employing a current value before a high inrush current flows, in other words, a current value that can be measured with the small full-scale current sensor, when it is determined that a starter switch is turned into an on-state.